taxicab vs motorcar

taxicab and motorcar both are nouns.

Word	Noun	Adjective	Verb	Adverb
taxicab	Yes	No	No	No
motorcar	Yes	No	No	No

As nouns, motorcar is a hypernym of taxicab; that is, motorcar is a word with a broader meaning than taxicab:

taxicab: a car driven by a person whose job is to take passengers where they want to go in exchange for money
motorcar: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other hypernyms of taxicab include auto, automobile, car, machine.

taxicab (noun)	motorcar (noun)
a car driven by a person whose job is to take passengers where they want to go in exchange for money	a motor vehicle with four wheels; usually propelled by an internal combustion engine